Biotransformation of methane at landfill sites can be estimated by applying compound specific stable isotope analysis of methane from the anaerobic and the cover layer surface zone. Next to these two input parameters, merely the knowledge of the carbon isotopic fractionation of the bacterial methane oxidation in terms of the enrichment factor (ε) is required. However, many factors and conditions have been described to affect ε. These include temperature, the applied landfill cover, the type of expressed methane monooxygenase (MMO), and cell density.

In this work we investigated the microbial methane oxidation with respect to temperature and type of methanotrophic enrichment culture. A newly designed setup was used to overcome potential CH₄-substrate limitations such as diffusion that could affect the determined values of ε by improper and inhomogeneous mixing. The isotopic fractionation was determined based on the stable carbon isotope analysis of methane and carbon dioxide. The obtained value for isotopic fractionation was ε_22°C = -0.0136 ± 0.0036. Also for the first time, bulk stable isotope analysis of bacterial cell mass was performed by flow Microcentrifuge Tube injection analysis isotope ratio mass spectrometry.

Sorption of PFOA onto different laboratory materials: Filter membranes and centrifuge tubes.

• Measurement and reporting of concentrations of contaminants of emerging concern such as per- and polyfluoroalkyl substances (PFASs), including perfluorooctanoic acid (PFOA), is an integral part of most investigations.
• Occurrence of sorption losses of PFAS analytes onto particular laboratory-ware (e.g. glass containers) has been suggested in the published literature but has not been investigated in detail.
• We examined sorption losses from aqueous PFOA solutions in contact with different commonly-used materials in filter units and centrifuge tubes (glass and plastics).
• Sorption of PFOA onto different filter membrane types ranged from 21-79% indicating that filtration can introduce a major source of error in PFOA analysis; pre-treatment of filter membranes with phosphate or methanol solutions did not improve PFOA recovery. Substantial adsorption of PFOA was also observed on tubes made from polypropylene (PP), polystyrene (PS), polycarbonate (PC), and glass where losses observed were between 32-45%, 27-35%, 16-31% and 14-24%, respectively.
• Contrary to suggestions in the literature, our results indicated that the greatest sorption losses for PFOA occurred on PP, whereas losses on glass tubes were much lower. Variations in ionic strength and pH did not greatly influence PFOA recovery.
• When PFOA concentrations were increased, the percent recovery of PFOA increased, indicating that binding sites on tube-walls were saturable. This study draws attention towards analytical bias that can occur due to sorption losses during routine procedures, and highlights the importance of testing the suitability of chosen laboratory-ware for specific PFAS analytes of interest prior to experimental use.
• The centrifuge is among the oldest and most widely used pieces of laboratory equipment, with significant applications that include clinical diagnostics and biomedical research. A major limitation of laboratory centrifuges is their “black box” nature, limiting sample observation to before and after centrifugation. Thus, optimized protocols require significant trial and error, while unoptimized protocols waste time by centrifuging longer than necessary or material due to incomplete sedimentation.
• Here, we developed an instrumented centrifuge tube receptacle compatible with several commercial benchtop centrifuges that can provide real-time sample analysis during centrifugation. We demonstrated the system by monitoring cell separations during centrifugation for different spin speeds, concentrations, buffers, cell types, and temperatures. We show that the collected data are valuable for analytical purposes (e.g. quality control), or as feedback to the user or the instrument.
• For the latter, we verified an adaptation where complete sedimentation turned off the centrifuge and notified the user by a text message. Our system adds new functionality to existing laboratory centrifuges, saving users time and providing useful feedback. This add-on potentially enables new analytical applications for an instrument that has remained largely unchanged for decades.

Influence of the centrifuge time of primary plasma tubes on routine coagulation testing.

Preparation of blood specimens is a major bottleneck in the laboratory throughput. Reliable strategies for reducing the time required for specimen processing without affecting quality should be acknowledged, especially for laboratories performing stat analyses. The present investigation was planned to establish a minimal suitable centrifuge time for primary samples collected for routine coagulation testing.

Five sequential primary vacuum tubes containing 0.109 mol/l buffered trisodium citrate were collected from 10 volunteers and were immediately centrifuged on a conventional centrifuge at 1500 x g, at room temperature for 1, 2, 5, 10 and 15 min, respectively. Hematological and routine coagulation testing, including prothrombin time, activated partial thromboplastin time and fibrinogen, were performed. The centrifugation time was inversely associated with residual blood cell elements in plasma, especially platelets. Statistically significant variations from the reference 15-min centrifuge specimens were observed for fibrinogen in samples centrifuged for 5 min at most and for the activated partial thromboplastin time in samples centrifuged for 2 min at most.

Meaningful biases related to the desirable bias were observed for fibrinogen in samples centrifuged for 2 min at most, and for the activated partial thromboplastin time in samples centrifuged for 1 min at most. According to our experimental conditions, a 5-10 min centrifuge time at 1500 x g may be suitable for primary tubes collected for routine coagulation testing.

We quantified the formed elements of urine sediment using newly designed plastic centrifuge tubes with top and bottom openings and a 0.5 ml sized bottom ball (YZ tube).

This design minimizes the adherence of formed elements that occurs on the glass surface of conventional tubes. The numbers of white blood cells (WBC) and red blood cells (RBC) using glass tubes did not differ from those observed using YZ tubes. However, the YZ tube method detected renal casts more frequently than the conventional glass tube method; the detection rate for renal casts in normal urine samples was 21.4% vs 2.9%, in samples from hospitalized patients it was 47.5% vs 10.2%, and from patients with kidney disease it was 88.9% vs. 44.4%. Especially, the YZ tube method detected more hyaline casts in all types of samples.

The correlation between the glass tube and YZ tube methods was good for WBC (r=0.996), RBC (r=0.964), and epithelial cell count (r=0.939), but the correlation was weak for casts (r=0.511 for hyaline casts; r=0.359 for other casts). In conclusion, the YZ tube method of urine sediment analyses is an easy and accurate quantitative method; it is recommended as the method of choice for detecting and quantifying pathological casts in urine